The overall objective of this proposal to determine how expression of enteric peptides is differentially regulated by physiological agents. Secretion and biosynthesis of enteric peptides have been independently investigated, however, there is little understanding of the mechanisms coupling peptide release and expression. Studying regulated expression in the intestine is particularly challenging because enteric peptides are modulated not only by hormones and transmitters, but also by nutritional substrates. Additionally, the tissue-specific expression of peptides in both enteric neurons and endocrine cells suggests that complex regulatory mechanisms exist. To directly study the regulation of enteric peptides at the cell level, we have developed 2 primary culture systems comprised of neurotensin/neuromedin N (NT/N)-containing 1) mucosal endocrine cells and 2) submucosal neurons. Work currently sponsored in our laboratory is directed towards characterizing the role of cAMP and calcium in transducing secretagogue regulation of NT/N release in cell cultures. Recently, we used these culture systems to clone cDNAs encoding NT/N, allowing us to extend our studies on NT/N cells to the molecular level. This proposal complements our current work by defining transcriptional and translational effects of secretagogues on NT/N expression. Studies using both whole animals and enteric cell cultures will investigate: 1) nutrient (fatty acid and glucose) regulation of NT/N expression, 2) hormone and transmitter regulation of NT/N expression, and 3) tissue-specific mechanisms regulating the expression and processing of NT/N transcripts in mucosal endocrine cells and submucosal neurons. The results of this investigation will answer important questions regarding the physiologic expression of an enteric peptide that acts as both a hormone and neurotransitter to regulate digestive function.